This invention relates to reel to reel tape recorder systems. More specifically this invention deals with improved tape tensioning as speed maintaining devices. Reel to reel recorders have been the subject of continued research into improving the mechanical-electrical interface to achieve greater reliability and improved performance.
One of the crucial aspects of performance is the requirement that the tape be driven past the heads at an extremely uniform speed and under the necessary tension to insure that the head-tape interface is maintained. Many such systems are known, a popular type using pinch rollers to achieve contact pressure with a drive capstan. Such systems, while generally effective, tend to stretch the tape and involve contact pressure on the magnetic sensitive surface. The use of pinch rollers therefore presents some undesirable problems. Accordingly, a second system, the frictional force drive capstan, has been the subject of study and potential commercial use.
A typical prior art device is shown in FIG. 1. As shown therein the principle of a frictional force drive capstan system tape recorder is such that, in order to stabilize and increase the frictional forces between a tape 3 and a capstan 1 and an idler 2, the winding angles of the tape 3 with respect to the capstan 1 and the idler 2 are increased by means of rollers 6' and 7' which are rotatably mounted on the ends of arms 4' and 5', respectively. In the frictional force drive capstan system tape recorder, unlike an ordinary tape recorder, no pinch roller is used to run the tape.
One of the problems of such systems is the setting of proper tension on the tape by settings of displacement of the arms 4' and 5' for different modes of operation. Additionally, during the course of a particular operation, the tape tension must be maintained constant, thereby imposing a real-time monitoring requirement.
Another requirement in reel to reel recorders is the necessity to sense an end of tape condition. In such recorders, the fast winding or play conditions should be terminated when this condition exist and well known techniques utilize a signal or metal strip placed on the tape at a predetermined end location. A sensor is employed to specifically monitor this condition and stop the drive motor action when sensed. While effective, these techniques require an additional detector for end of tape sensing.
In friction force systems, the loading of tape can be difficult if the force applying arms are positioned in a tension application position. However, if the arms are moved for tape loading, tension must be maintained for constant pressure maintenance during operation. Moreover, tape tension is a function of the operation performed. Accordingly, if the tension is to be maintained despite movement of the arms, such adjustment must be related to and carried out in association with a specific recorder function. This is done by varying take-up motor speed to maintain uniform tension.
Additionally in such systems, tape shifting devices are used to change the direction of the tape, particularly when it passes the heads. However, in some operations, such as fast winding, tension loss occurs resulting in the stretching of the tape, or making it difficult to accomplish uniform winding.